Methods of sealing expandable pipe in well bores and sealing compositions

ABSTRACT

The present invention provides methods and compressible foamed sealing compositions for sealing expandable pipe in well bores. The compressible sealant compositions for sealing expandable pipe are basically comprised of a hydraulic cement, a rubber latex, a rubber latex stabilizer, a gas and a mixture of foaming and foam stabilizing surfactants.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to methods and compressible sealantcompositions for sealing expandable pipe in well bores.

[0003] 2. Description of the Prior Art

[0004] A new well completion practice has been developed whereby casingsand liners are expanded diametrically after they are placed in wellbores. Prior to the expansion, a sealing composition is placed in theannulus between the walls of the well bore and the unexpanded casing orliner. A problem which can be encountered involves the use of hydrauliccement compositions as the sealing composition. Hydraulic cementcompositions are non-compressible and tend to resists the expansion ofthe casing or liner making the expansion more difficult. In addition, ifthe cement composition gels or sets prior to when the expansion isaccomplished, the cement composition is crushed in the annular spacebetween the walls of the well bore and the expandable casing or linerwhereby it does not function to seal the expanded casing or liner in thewell bore.

[0005] Thus, there are needs for improved sealant compositions forsealing expandable casings or liners in well bores which arecompressible and maintain the properties required to provide a sealbetween the walls of the well bore and the expanded casings or liners.

SUMMARY OF THE INVENTION

[0006] The present invention provides methods of sealing expandablecasings and liners in well bores and compressible sealant compositions.A method of the present invention for sealing an expandable pipe or pipestring such as a casing or liner in a well bore is basically comprisedof the following steps. The expandable pipe or pipe string is placed inthe well bore. A compressible hydraulic cement sealant composition whichremains competent when compressed is placed in the annulus between thewell bore and the pipe or pipe string. The sealant composition isallowed to harden into an impermeable mass and thereafter, theexpandable pipe or pipe string is expanded whereby the hardened sealantcomposition is compressed.

[0007] Another method of the invention for sealing expandable pipe orpipe strings is basically comprised of the following steps. Acompressible foamed sealant composition is provided comprised of ahydraulic cement, a rubber latex, a rubber latex stabilizer, a gas and amixture of foaming and foam stabilizing surfactants. An expandable pipeor pipe string is placed in the well bore and the compressible foamedsealant composition is placed in the annulus between the well bore andthe expandable pipe or pipe string. The foamed sealant composition isallowed to harden into an impermeable mass, and thereafter, theexpandable pipe or pipe string is expanded whereby the hardened foamedsealant composition is compressed.

[0008] The compressible foamed sealant compositions of this inventionwhich remain competent when compressed are basically comprised of ahydraulic cement, a rubber latex, a rubber latex stabilizer, a gas and amixture of foaming and foam stabilizing surfactants.

[0009] The amount of gas included in the compressible foamed sealantcomposition is such that the gas volume is substantially equal to theexpansion volume of the expandable casings or liners. This allows thehardened sealant composition to be compressed while maintaining itsintegrity and sealant properties.

[0010] The objects, features and advantages of the present inventionwill be readily apparent to those skilled in the art upon a reading ofthe description of preferred embodiments which follows.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0011] The present invention provides compressible hydraulic cementsealant compositions which remain competent when compressed. That is,when a compressible hydraulic cement composition of this invention isused for sealing an expandable pipe or pipe string in a well bore, thecomposition is placed in the annulus between the expandable pipe and thewell bore, it is allowed to harden therein and when the expandable pipeis expanded, the sealant composition is compressed and retains itscompetency, i.e., continues to support and seal the pipe. Methods ofusing the compositions are also provided.

[0012] The compressible sealant compositions of this invention arebasically comprised of a hydraulic cement, a rubber latex, a rubberlatex stabilizer, a gas and a mixture of foaming and foam stabilizingsurfactants. The compressible foamed sealant compositions arecompressible after hardening to the extent that the compositions containgas. Thus, the volume of gas utilized in the sealant compositions aresubstantially equal to the volume reduction of the annular spacecontaining the sealant composition.

[0013] Examples of the hydraulic cement that can be utilized inaccordance with this invention, include, but are not limited to, calciumaluminate cement, Portland cement, and Portland blast furnace cement. Ofthese, calcium aluminate cement is preferred.

[0014] A variety of well known rubber latexes can be utilized inaccordance with the present invention such as styrene/butadienecopolymer latex emulsion, polychloroprene emulsion, polyisopreneemulsion and acrylonitrilibutadiene emulsion. Of these,styrene/butadiene latex emulsion is preferred. The styrene/butadienelatex emulsion can include in the range of from about 40% to about 70%water by weight of the latex. The weight ratio of styrene to butadienein the latex can range from about 10%:90% to about 90%:10%. A preferredstyrene/butadiene aqueous latex for use in accordance with the presentinvention contains water in an amount of about 50% by weight of thelatex and has a weight ratio of styrene to butadiene in the latex ofabout 25%:75%. A latex of this type is commercially available fromHalliburton Energy Services, Inc. of Duncan, Oklahoma under the tradedesignation “LATEX 2000™.” The rubber latex utilized is included in thefoamed sealant composition of this invention in an amount in the rangeof from about 80% to about 300% by weight of the calcium aluminatecement therein.

[0015] In order to prevent the aqueous latex from prematurelycoagulating and increasing the viscosity of the foamed sealantcomposition, an effective amount of a latex stabilizing surfactant isincluded in the composition. Latex stabilizing surfactants which aresuitable for use in accordance with this invention are surfactantshaving the formula R—Ph—O(OCH₂CH₂)_(m)OH wherein R is an alkyl grouphaving from about 5 to about 30 carbon atoms, Ph is phenyl and m is aninteger of from about 5 to about 50. A preferred surfactant in the abovedefined group is ethoxylated nonylphenyl containing in the range of fromabout 20 to about 30 moles of ethylene oxide.

[0016] Another suitable surfactant is a salt having the formulaR₁(R₂O)_(n)SO₃X wherein R₁ is an alkyl group having from about 5 toabout 20 carbon atoms, R₂ is the group —CH₂—CH₂—, n is an integer fromabout 10 to about 40 and X is a cation. A particularly preferredsurfactant of this type is the sodium salt of a sulfonated compoundderived by reacting a C₁₂₋₁₅ alcohol with about 15 moles of ethyleneoxide having the formula H(CH₂)₁₂₋₁₅(CH₂CH₂O)₁₅SO₃Na which iscommercially available under the trade designation name “AVANEL S150™”from PPG Mazer, Mazer Chemicals, a Division of PPG Industries, Inc. ofGurnee, Ill.

[0017] The latex stabilizing surfactant utilized is included in thefoamed sealant composition in an amount in the range of from about 3% toabout 6% by weight of the rubber latex in the foamed sealantcomposition, preferably in an amount of 4%.

[0018] The gas in the compressible foamed sealant composition can be airor nitrogen with nitrogen being preferred. The gas is present in thefoamed sealant composition in an amount in the range of from about 5% toabout 35% by volume of the non-foamed sealant composition. As mentionedabove, the volume of gas used in the foamed sealant composition isgenerally substantially equal to the volume of decrease in the annulusbetween the walls of the well bore and the expandable pipe when theexpandable pipe is expanded.

[0019] Various mixtures of foaming and foam stabilizing surfactants canbe utilized in the compressible foamed sealant compositions of thisinvention. One such mixture is comprised of about 2 parts by weight ofan alpha-olefinic sulfonate surfactant having the formulaH(CH₂)_(n)—CH═CH—(CH₂)_(m)SO₃Na wherein n and m are individuallyintegers in the range of from about 6 to about 16 and about 1 part byweight of a betaine surfactant having the formulaR—CONHCH₂CH₂CH₂N⁺(CH₃)₂CH₂CO₂ ⁻ wherein R is a radical selected from thegroup of decyl, cetyl, oleyl, lauryl and cocoyl. This mixture isdescribed in detail in U.S. Pat. No. 5,897,699 issued to Chatterji etal. on Apr. 27, 1999 which is incorporated herein by reference thereto.

[0020] Another particularly preferred mixture of foaming and foamstabilizing surfactants is comprised of about 63.3 parts by weight of anethoxylated alcohol ether sulfate surfactant of the formulaH(CH₂)a(OC₂H₄)bOSO₃NH₄ ⁺wherein a is an integer in the range of fromabout 6 to about 10 and b is an integer in the range of from about 3 toabout 10, 31.7 parts by weight of an alkyl or alkene amidopropyl betainesurfactant having the formula R—CONHCH₂CH₂CH₂N⁺(CH₃)₂CH₂CO₂ ⁻ wherein Ris a radical selected from the group of decyl, cocoyl, lauryl, cetyl andoleyl and about 5 parts by weight of an alkyl or alkene amidopropyldimethyl amine oxide surfactant having the formulaR—CONHCH₂CH₂CH₂N⁺(CH₃)₂O⁻ wherein R is a radical selected from the groupof decyl, cocoyl, lauryl, cetyl and oleyl. This mixture is described indetail in U.S. Pat. No. 6,063,738 issued to Chatterji et al. on May 16,2000 which is incorporated herein by reference thereto.

[0021] Of the above mixtures of foaming and foam stabilizingsurfactants, a mixture of an ethoxylated alcohol ether sulfatesurfactant, an alkyl or alkene amidopropyl betaine surfactant and analkyl or alkene amidopropyl dimethyl amine oxide surfactant ispreferred.

[0022] The mixture of foaming and foam stabilizing surfactants isincluded in the compressible foamed sealant composition of thisinvention in an amount in the range of from about 4% to about 10% byvolume of the rubber latex therein, preferably in an amount of about 6%.

[0023] The compressible foamed sealant composition can also include aviscosity increasing agent for suspending particulate solids therein. Avariety of viscosity increasing agents also known as gelling agents canbe utilized including, but not limited to, bentonite,hydroxyethylcellulose, sodium silicate and guar gum. Of these, bentoniteis preferred.

[0024] When used, the viscosity increasing agent is included in thecompressible foamed sealant composition in an amount in the range offrom about 5% to about 10% by weight of cement therein, preferably in anamount of 7%.

[0025] The compressible foamed sealant composition can also include aparticulate solid density adjusting weighting material suspendedtherein. A variety of weighting materials can be utilized including, butnot limited to, iron oxide, barium sulfate, galena and manganese oxide.Of these, iron oxide is preferred.

[0026] When used, the density adjusting weighting material is includedin the compressible foamed sealant composition in an amount in the rangeof from about 1% to about 250% by weight of cement therein.

[0027] The compressible foamed sealant composition can also include aset retarder. Examples of set retarders which can be used include, butare not limited to, citric acid, sodium gluconate, gluconic acid, sodiumcitrate and sugar. Of these, citric acid is preferred.

[0028] When used, the set retarder is included in the compressiblefoamed sealant composition in an amount in the range of from about 0.2%to about 4% by weight of cement therein, preferably in an amount ofabout 1%.

[0029] As is well known to those skilled in the art, a variety of otherconventional additives can be utilized in the compressible foamedsealant composition of this invention including, but not limited to,fluid loss control additives, accelerators, dispersants and lostcirculation materials.

[0030] A method of the present invention for sealing an expandable pipeor pipe string such as a casing or liner in a well bore is basicallycomprised of the following steps. The expandable pipe or pipe string isplaced in the well bore. A compressible hydraulic cement sealantcomposition which remains competent when compressed is placed in theannulus between the well bore and the expandable pipe or pipe string.The sealant composition is allowed to harden into an impermeable massand thereafter, the expandable pipe or pipe string is expanded wherebythe hardened sealant composition is compressed.

[0031] Another method of this invention for sealing an expandable pipeor pipe string in a well bore is basically comprised of the followingsteps. A compressible sealant composition is provided comprised of ahydraulic cement, a rubber latex, a rubber latex stabilizer, a gas and amixture of foaming and foam stabilizing surfactants. An expandable pipeor pipe string is placed in the well bore. The compressible foamedsealant composition is then placed in the annulus between the well boreand the expandable pipe or pipe string and the foamed sealantcomposition is allowed to harden into an impermeable mass therein.Thereafter, the expandable pipe or pipe string is expanded whereby thehardened foamed sealant composition is compressed.

[0032] The hydraulic cement, rubber latex, rubber latex stabilizer andmixture of foaming and foam stabilizing surfactants are as describedabove and are included in the compressible foamed sealant composition inthe amounts set forth above. The gas is also as described above and isincluded in the compressible foamed sealant composition in the generalamount set forth above. However, as also mentioned above, the gas usedis included in the compressible foamed sealant composition in a volumeamount which is substantially the same as the volume decrease in theannulus between the walls of the well bore and the expandable pipe whenthe expandable pipe is expanded. The expansion of the expandable pipecompresses the gas in the foamed sealant composition but the compositionmaintains its competency, i.e., its integrity and sealing properties,whereby it prevents the undesirable migration of fluids between zones orformations penetrated by the well bore and physically supports andpositions the pipe in the well bore.

[0033] A preferred compressible foamed sealant composition for sealingan expandable pipe or pipe string in a well bore is comprised of: ahydraulic cement; a rubber latex; a rubber latex stabilizer; a gas; anda mixture of foaming and foam stabilizing surfactants.

[0034] As mentioned, the compressible foamed sealant composition whenrequired also includes a viscosity increasing agent, a density adjustingweighting material, a cement retarder and other conventional additives.

[0035] A preferred method of this invention for sealing an expandablepipe or pipe string in a well bore is comprised of the steps of: (a)providing a compressible foamed sealant composition comprised of ahydraulic cement; a rubber latex, a rubber latex stabilizer, a gas and amixture of foaming and foam stabilizing surfactants; (b) placing theexpandable pipe or pipe string in the well bore; (c) placing thecompressible foamed sealant composition in the annulus between the wellbore and the expandable pipe or pipe string; (d) allowing the foamedsealant composition to harden into an impermeable mass; and (e)expanding the expandable pipe or pipe string whereby the hardened foamedsealant composition is compressed.

[0036] Another preferred method of this invention for sealing anexpandable pipe or pipe string in a well bore is comprised of the stepsof: (a) providing a compressible foamed sealant composition comprised ofcalcium aluminate cement, a rubber latex comprised of astyrene/butadiene copolymer latex emulsion containing water in an amountof about 50% by weight of the latex and being present in the foamedsealant composition in an amount in the range of from about 80% to about300% by weight of the calcium aluminate cement therein, a rubber latexstabilizer comprised of a surfactant having the formulaH(CH₂)₁₂₋₁₅(CH₂CH₂O)₁₅SO₃Na present in the foamed sealant composition inan amount in the range of from about 3% to about 6% by weight of therubber latex therein, nitrogen gas present in the foamed sealantcomposition in an amount in the range of from about 5% to about 35% byvolume of the non-foamed sealant composition and a mixture of foamingand foam stabilizing surfactants comprised of a mixture of about 63.3parts by weight of an ethoxylated alcohol ether sulfate surfactant,about 31.7 parts by weight of a cocoyl amidopropyl betaine surfactantand about 5 parts by weight of a cocoyl amidopropyl dimethyl amine oxidesurfactant present in the foamed sealant composition in an amount in therange of from about 4% to about 10% by volume of the rubber latextherein; (b) placing the expandable pipe or pipe string in the wellbore; (c) placing the compressible foamed sealant composition in theannulus between the well bore and the expandable pipe or pipe string;(d) allowing the foamed sealant composition to harden into animpermeable mass; and (e) expanding the expandable pipe or pipe stringwhereby the hardened foamed sealant composition is compressed.

[0037] As mentioned above, the foamed sealant composition can furthercomprise bentonite present in the foamed sealant composition in anamount in the range of from about 5% to about 10% by weight of cementtherein, an iron oxide weighting material present in the foamed sealantcomposition in an amount in the range of from about 1% to about 250% byweight of cement therein and a citric acid cement set retarder presentin the foamed sealant composition in an amount of about 1% by weight ofcement therein.

[0038] In order to further illustrate the compressible foamed sealantcompositions and methods of this invention, the following example isgiven.

EXAMPLE

[0039] A compressible foamed sealant composition of this invention wasprepared by first mixing calcium aluminate cement with a rubber latexcomprised of a styrene/butadiene copolymer latex emulsion containingwater in an amount of about 50% by weight of the latex present in theresulting slurry in an amount of about 221% by weight of the cementtherein, a rubber latex stabilizer comprised of a surfactant having theformula H(CH₂)₁₂₋₁₅(CH₂CH₂O)₁₅SO₃Na was added to the slurry in an amountof about 4% by weight of the rubber latex therein, a mixture of foamingand foam stabilizing surfactants comprised of about 63.3 parts by weightof an ethoxylated alcohol ether sulfate surfactant, about 31.7 parts byweight of a cocoyl amidopropyl betaine surfactant and about 5 parts byweight of a cocoyl amidopropyl dimethyl amine oxide surfactant was addedto the slurry in an amount of about 6% by volume of the rubber latex inthe slurry, bentonite was added to the slurry in an amount of about 7%by weight of cement in the slurry, particulate solid iron oxide wasadded to the slurry in an amount of about 200% by weight of cement inthe slurry and a citric acid set retarder was added to the slurry in anamount of 1% by weight of cement in the slurry. The resulting slurrydensity was 14.45 pounds per gallon. The slurry was foamed so that 23.9%of air was entrained in the foamed slurry. The foamed slurry had adensity of 11 pounds per gallon. The thickening time of the foamedslurry was 3 hours and 22 minutes at 91° F. After being allowed toharden for 24 hours in a closed container in a 110° F. water bath, thefoamed cement slurry was compressed by 25% by the application of 1,425psi to a piston located on top of the closed container. When the samplewas then removed from the container it was tested for compressivestrength which was 120 psi. A foamed Portland cement mixture was testedunder the same conditions and in the same way as described above for thecompressible foamed sealant composition of this invention. The Portlandcement was crushed during the volume reduction of the experiment.

[0040] Thus, the present invention is well adapted to carry out theobjects and attain the ends and advantages mentioned as well as thosewhich are inherent therein. While numerous changes may be made by thoseskilled in the art, such changes are encompassed within the spirit ofthis invention as defined by the appended claims.

What is claimed is:
 1. A method of sealing an expandable pipe or pipe string in a well bore comprising the steps of: (a) placing said expandable pipe or pipe string in said well bore; (b) placing a compressible hydraulic cement sealant composition which remains competent when compressed in the annulus between said well bore and said expandable pipe or pipe string; (c) allowing said sealant composition to harden into an impermeable mass; and (d) expanding said expandable pipe or pipe string whereby said hardened sealant composition is compressed.
 2. The method of claim 1 wherein said compressible hydraulic cement sealant composition is comprised of a hydraulic cement, a rubber latex, a rubber latex stabilizer, a gas and a mixture of foaming and foam stabilizing surfactants.
 3. The method of claim 2 wherein said hydraulic cement is selected from the group consisting of calcium aluminate cement, Portland cement and Portland blast furnace cement.
 4. The method of claim 2 wherein said hydraulic cement is calcium aluminate cement.
 5. The method of claim 2 wherein said rubber latex is selected from the group consisting of a styrene/butadiene copolymer latex emulsion, polychloroprene emulsion, polyisoprene emulsion and acrylonitrilibutadiene emulsion.
 6. The method of claim 2 wherein said rubber latex is a styrene/butadiene copolymer latex emulsion containing water in an amount in the range of from about 40% to about 70% by weight of said latex.
 7. The method of claim 2 wherein said rubber latex is present in said sealant composition in an amount in the range of from about 80% to about 300% by weight of said cement therein.
 8. The method of claim 2 wherein said rubber latex stabilizer is selected from the group consisting of surfactants having the formula R—Ph—O(OCH₂CH₂)_(m)OH wherein R is an alkyl group having from about 5 to about 30 carbon atoms, pH is phenyl and m is an integer of from about 5 to about 50 and surfactants having the formula R₁(R₂O)_(n)SO₃X wherein R₁ is an alkyl group having from about 5 to about 20 carbon atoms, R₂ is the group —CH₂—CH₂—, n is an integer from about 10 to about 40 and X is a cation.
 9. The method of claim 2 wherein said rubber latex stabilizer is a surfactant having the formula H(CH₂)₁₂₋₁₅(CH₂CH₂O)₁₅SO₃Na.
 10. The method of claim 2 wherein said rubber latex stabilizer is present in said sealant composition in an amount in the range of from about 3% to about 6% by weight of rubber latex therein.
 11. The method of claim 2 wherein said gas is selected from the group consisting of air and nitrogen.
 12. The method of claim 2 wherein said gas is nitrogen.
 13. The method of claim 2 wherein said gas is present in said sealant composition in an amount in the range of from about 5% to about 35% by volume of said non-foamed sealant composition.
 14. The method of claim 2 wherein said mixture of foaming and foam stabilizing surfactants is a mixture of an ethoxylated alcohol ether sulfate surfactant, an alkyl or alkene amidopropyl betaine surfactant and an alkyl or alkene amidopropyl dimethyl amine oxide surfactant.
 15. The method of claim 2 wherein said mixture of foaming and foam stabilizing surfactants is present in said sealant composition in an amount in the range of from about 4% to about 10% by volume of said rubber latex therein.
 16. The method of claim 2 wherein said sealant composition further comprises a viscosity increasing agent.
 17. The method of claim 16 wherein said viscosity increasing agent is selected from the group consisting of bentonite, hydroxyethyl cellulose, sodium silicate and guar gum.
 18. The method of claim 16 wherein said viscosity increasing agent is bentonite.
 19. The method of claim 16 wherein said viscosity increasing agent is present in said sealant composition in an amount in the range of from about 5% to about 10% by weight of cement therein.
 20. The method of claim 2 wherein said sealant composition further comprises a density adjusting weighting material.
 21. The method of claim 20 wherein said density adjusting weighting material is selected from the group consisting of particulate iron oxide, barium sulfate, galena and manganese oxide.
 22. The method of claim 20 wherein said density adjusting weighting material is particulate iron oxide.
 23. The method of claim 20 wherein said density adjusting weighting material is present in said sealant composition in an amount in the range of from about 1% to about 250% by weight of cement therein.
 24. The method of claim 2 wherein said sealant composition further comprises a cement set retarder.
 25. The method of claim 24 wherein said cement set retarder is selected from the group consisting of citric acid, sodium gluconate, gluconic acid, sodium citrate and sugar.
 26. The method of claim 24 wherein said cement set retarder is citric acid.
 27. The method of claim 24 wherein said set retarder is present in said sealant composition in an amount in the range of from about 0.2% to about 4% by weight of cement therein.
 28. A method of sealing an expandable pipe or pipe string in a well bore comprising the steps of: (a) providing a compressible foamed sealant composition comprised of a hydraulic cement, a rubber latex, a rubber latex stabilizer, a gas and a mixture of foaming and foam stabilizing surfactants; (b) placing said expandable pipe or pipe string in said well bore; (c) placing said compressible foamed sealant composition in the annulus between said well bore and said expandable pipe or pipe string; (d) allowing said foamed sealant composition to harden into an impermeable mass; and (e) expanding said expandable pipe or pipe string whereby said hardened foamed sealant composition is compressed.
 29. The method of claim 28 wherein said hydraulic cement is selected from the group consisting of calcium aluminate cement, Portland cement and Portland blast furnace cement.
 30. The method of claim 28 wherein said hydraulic cement is calcium aluminate cement.
 31. The method of claim 28 wherein said rubber latex is selected from the group consisting of a styrene/butadiene copolymer latex emulsion, polychloroprene emulsion, polyisoprene emulsion and acrylonitrilibutadiene emulsion.
 32. The method of claim 28 wherein said rubber latex is a styrene/butadiene copolymer latex emulsion containing water in an amount in the range of from about 40% to about 70% by weight of said latex.
 33. The method of claim 28 wherein said rubber latex is present in said foamed sealant composition in an amount in the range of from about 80% to about 300% by weight of said cement therein.
 34. The method of claim 28 wherein said rubber latex stabilizer is selected from the group consisting of surfactants having the formula R—Ph—O(OCH₂CH₂)_(m)OH wherein R is an alkyl group having from about 5 to about 30 carbon atoms, pH is phenyl and m is an integer of from about 5 to about 50 and surfactants having the formula R₁(R₂O)_(n)SO₃X wherein R₁ is an alkyl group having from about 5 to about 20 carbon atoms, R₂ is the group —CH₂—CH₂—, n is an integer from about 10 to about 40 and X is a cation.
 35. The method of claim 28 wherein said rubber latex stabilizer is a surfactant having the formula H(CH₂)₁₂₋₁₅(CH₂CH₂O)₁₅SO₃Na.
 36. The method of claim 28 wherein said rubber latex stabilizer is present in said foamed sealant composition in an amount in the range of from about 3% to about 6% by weight of rubber latex therein.
 37. The method of claim 28 wherein said gas is selected from the group consisting of air and nitrogen.
 38. The method of claim 28 wherein said gas is nitrogen.
 39. The method of claim 28 wherein said gas is present in said foamed sealant composition in an amount in the range of from about 5% to about 35% by volume of said non-foamed sealant composition.
 40. The method of claim 28 wherein said mixture of foaming and foam stabilizing surfactants is a mixture of an ethoxylated alcohol ether sulfate surfactant, an alkyl or alkene amidopropyl betaine surfactant and an alkyl or alkene amidopropyl dimethyl amine oxide surfactant.
 41. The method of claim 28 wherein said mixture of foaming and foam stabilizing surfactants is present in said foamed sealant composition in an amount in the range of from about 4% to about 10% by volume of said rubber latex therein.
 42. The method of claim 28 wherein said foamed sealant composition further comprises a viscosity increasing agent.
 43. The method of claim 42 wherein said viscosity increasing agent is selected from the group consisting of bentonite, hydroxyethyl cellulose, sodium silicate and guar gum.
 44. The method of claim 42 wherein said viscosity increasing agent is bentonite.
 45. The method of claim 42 wherein said viscosity increasing agent is present in said foamed sealant composition in an amount in the range of from about 5% to about 10% by weight of cement therein.
 46. The method of claim 28 wherein said foamed sealant composition further comprises a density adjusting weighting material.
 47. The method of claim 46 wherein said density adjusting weighting material is selected from the group consisting of particulate iron oxide, barium sulfate, galena and manganese oxide.
 48. The method of claim 46 wherein said density adjusting weighting material is particulate iron oxide.
 49. The method of claim 46 wherein said density adjusting weighting material is present in said foamed sealant composition in an amount in the range of from about 1% to about 250% by weight of cement therein.
 50. The method of claim 28 wherein said foamed sealant composition further comprises a cement set retarder.
 51. The method of claim 50 wherein said cement set retarder is selected from the group consisting of citric acid, sodium gluconate, gluconic acid, sodium citrate and sugar.
 52. The method of claim 50 wherein said cement set retarder is citric acid.
 53. The method of claim 50 wherein said set retarder is present in said foamed sealant composition in an amount in the range of from about 0.2% to about 4% by weight of cement therein.
 54. A method of sealing an expandable pipe or pipe string in a well bore comprising the steps of: (a) providing a compressible foamed sealant composition comprised of calcium aluminate cement, a rubber latex comprised of a styrene/butadiene copolymer latex emulsion containing water in an amount of about 50% by weight of said latex and being present in said foamed sealant composition in an amount in the range of from about 80% to about 300% by weight of said cement therein, a rubber latex stabilizer comprised of a surfactant having the formula H(CH₂)₁₂₋₁₅(CH₂CH₂O)₁₅SO₃Na present in said sealant composition in an amount in the range of from about 3% to about 6% by weight of said rubber latex therein, nitrogen gas present in said foamed sealant composition in an amount in the range of from about 5% to about 35% by volume of said non-foamed sealant composition and a mixture of foaming and foam stabilizing surfactants comprised of about 63.3 parts by weight of an ethoxylated alcohol ether sulfate surfactant, about 31.7 parts by weight of a cocoyl amidopropyl betaine surfactant and about 5 parts by weight of a cocoyl amidopropyl dimethyl amine oxide surfactant present in said foamed sealant composition in an amount in the range of from about 4% to about 10% by volume of said rubber latex therein; (b) placing said expandable pipe or pipe string in said well bore; (c) placing said compressible foamed sealant composition in the annulus between said well bore and said expandable pipe or pipe string; (d) allowing said foamed sealant composition to harden into an impermeable mass; and (e) expanding said expandable pipe or pipe string whereby said hardened foamed sealant composition is compressed.
 55. The method of claim 54 wherein said foamed sealant composition further comprises bentonite present in said foamed sealant composition in an amount in the range of from about 5% to about 10% by weight of cement therein.
 56. The method of claim 55 wherein said foamed sealant composition further comprises iron oxide weighting material present in said foamed sealant composition in an amount in the range of from about 1% to about 250% by weight of cement therein.
 57. The method of claim 56 wherein said foamed sealant composition further comprises a citric acid cement set retarder present in said foamed sealant composition in an amount in the range of from about 0.2% to about 4% by weight of cement therein.
 58. A compressible foamed sealant composition for sealing an expandable pipe or pipe string in a well bore comprising: a hydraulic cement; a rubber latex; a rubber latex stabilizer; a gas; and a mixture of foaming and foam stabilizing surfactants.
 59. The composition of claim 58 wherein said hydraulic cement is selected from the group consisting of calcium aluminate cement, Portland cement and Portland blast furnace cement.
 60. The composition of claim 58 wherein said rubber latex is selected from the group consisting of a styrene/butadiene copolymer latex emulsion, polychloroprene emulsion, polyisoprene emulsion and acrylonitrilibutadiene.
 61. The composition of claim 58 wherein said rubber latex is present in said foamed sealant composition in an amount in the range of from about 80% to about 300% by weight of said cement therein.
 62. The composition of claim 58 wherein said rubber latex stabilizer is selected from the group consisting of surfactants having the formula R—Ph—O(OCH₂CH₂)_(m)OH wherein R is an alkyl group having from about 5 to about 30 carbon atoms, Ph is phenyl and m is an integer of from about 5 to about 50 and surfactants having the formula R₁(R₂O)_(n)SO₃X wherein R₁ is an alkyl group having from about 5 to about 20 carbon atoms, R₂ is the group —CH₂—CH₂—, n is an integer from about 10 to about 40 and X is a cation.
 63. The composition of claim 58 wherein said rubber latex stabilizer is present in said foamed sealant composition in an amount in the range of from about 3% to about 6% by weight of the rubber latex therein.
 64. The composition of claim 58 wherein said gas is selected from the group consisting of air and nitrogen.
 65. The composition of claim 58 wherein said gas is present in said foamed sealant composition in an amount in the range of from about 5% to about 35% by volume of said nonfoamed sealant composition.
 66. The composition of claim 58 wherein said mixture of foaming and foam stabilizing surfactants is a mixture of an ethoxylated alcohol ether sulfate surfactant, an alkyl or alkene amidopropyl betaine surfactant and an alkyl or alkene amidopropyl dimethyl amine oxide surfactant.
 67. The composition of claim 58 wherein said mixture of foaming and foam stabilizing surfactants is present in said foamed sealant composition in an amount in the range of from about 4% to about 10% by volume of said rubber latex therein.
 68. The composition of claim 58 wherein said foamed sealant composition further comprises a viscosity increasing agent.
 69. The composition of claim 68 wherein said viscosity increasing agent is selected from the group consisting of bentonite, hydroxyethyl cellulose, sodium silicate and guar gum.
 70. The composition of claim 68 wherein said viscosity increasing agent is present in said foamed sealant composition in an amount in the range of from about 5% to about 10% by weight of cement therein.
 71. The composition of claim 58 wherein said foamed sealant composition further comprises a density adjusting weighting material.
 72. The composition of claim 71 wherein said density adjusting weighting material is selected from the group consisting of particulate iron oxide, barium sulfate, galena and manganese oxide.
 73. The composition of claim 71 wherein said density adjusting weighting material is present in said foamed sealant composition in an amount in the range of from about 1% to about 250% by weight of cement therein.
 74. The composition of claim 58 wherein said foamed sealant composition further comprises a cement set retarder.
 75. The composition of claim 74 wherein said cement set retarder is selected from the group consisting of citric acid, sodium gluconate, gluconic acid, sodium citrate and sugar.
 76. The composition of claim 74 wherein said set retarder is present in said foamed sealant composition in an amount in the range of from about 0.2% to about 4% by weight of cement therein. 